The present invention is directed to an arrangement for venting an enclosure. More particularly, the present invention is directed to an arrangement for venting an enclosure wherein the enclosure is a bag containing toxic waste material.
The storage of waste materials, more particularly nuclear waste materials, is a vexing problem because the materials must be stored for a very long time. For example, nuclear waste must be stored for thousands of years. Temporary storage sites for nuclear waste are being filled at a rapid rate so nuclear waste materials must be transported to permanent and semi-permanent sites for disposal. Even at semi-permanent or permanent sites, there is concern that these materials may enter either the atmosphere or ground water so they must be stored in containers which minimize and hopefully eliminate leakage and the danger of the containers rupturing.
It is necessary to transport nuclear waste materials from nuclear waste producing sites to semi-permanent and permanent storage sites. It is desirable that containers having materials which might generate non-toxic, explosive gasses, such as hydrogen, be ventilated during transport. Accordingly, there is a need for an effective, inexpensive ventilation arrangement for these containers.
When storing and transporting plutonium waste, more plutonium waste can be stored safely in ventilated containers than unventilated containers. By utilizing ventilated containers, five to ten times more plutonium waste can be stored in a single container than can be stored if the containers are not ventilated. Accordingly, effectively ventilating containers so that explosive gasses can escape without also releasing radioactive material from the containers results in considerable cost savings.
In prior art arrangements, bags which are used as containers have utilized relatively rigid or stiff structures in order to hold filters in alignment with vent holes through the bags. Since these filters are stiff, they present discontinuities in a bag""s surface, which can generate localized stresses and which can interfere with sliding a bag into an outer rigid container. In view of these and other difficulties, there is a need to improve venting arrangements for containers that store waste material, especially nuclear waste material.
In view of the aforementioned considerations, the present invention is directed to an arrangement for venting an enclosure containing a material having an effluent associated therewith, wherein the container has a wall with an inside surface and an outside surface and has a vent hole through the surfaces. In accordance with the invention, a first film is adhered to the inside surface of the closure over the vent hole, the first film having a first aperture therethrough. A second of film is adhered to the outside surface of the enclosure over the vent hole, the second film having a second aperture therethrough and cooperating with the first film to define a chamber therebetween. A filter media is disposed in the chamber between the films, to filter particles and liquid from the effluent as the effluent passes therethrough, i.e., after the effluent enters the first aperture and before the effluent exits through the second aperture.
In a further aspect of the invention, the filter media, vent hole and apertures are aligned.
In still another aspect of the invention, the filter media is a resin material with a permanent electrical charge.
In a preferred embodiment of the invention, the filter media is comprised of split polypropylene fibers with a permanent electrical charge thereon.
In still a further embodiment of the invention, the enclosure is a bag made of a material such as polypropylene, polyurethane or polyvinylchloride.
In a further aspect of the invention, the bag and strips of film are made of polyurethane and the adhesive is an acrylic adhesive.
In a further aspect of the invention, the bag as previously described is placed in a rigid container, the rigid container preferably being made of stainless steel if the waste material is nuclear waste material.